Pioneering micro piling at Severn Tunnel junction provides ground stabilisation

Case Study

The busy approaches to the 7km-long Severn Tunnel have challenging ground conditions and a long standing problem with the subgrade. This was causing track quality issues that needed regular maintenance interventions and temporary speed restrictions as well as delivering an uncomfortable ride for train users.

Aspin’s micro piling solutions, pioneered in partnership with Network Rail and proven in other projects, provided a fast-acting and minimally invasive solution and are the subject of a comprehensive new, free Guide to Track Bed Micro Piling, produced by Network Rail Infrastructure Projects (IP) Track Engineering and Innovation Group. Nearly 200 new high integrity driven piles were created to three metres with a 275mm diameter pile cap, all fitting between the sleepers to provide a more solid foundation to support the track bed. There was no need to remove the tracks for the works for added speed and up to 30 piles were completed in one night’s work.

Project Overview Key Facts:

About Aspin: Aspin is a leader in the provision of high quality foundation, civil, geotechnical and structural engineering products and services for the rail, highways and infrastructure sectors.

Client: Network Rail Aspin Project Contact: Lee Healey

Client: Network Rail

Key Partners: Network Rail

Aspin contact: Lee Healey

Completion: 2017

Aspin Services:• Inspections & Investigations• Foundations & Piling• Consulting & Design

Working with Aspin, we were able to pioneer the concept of micro piling as a method of ground stabilisation in a railway environment, tackle deep-seated subgrade problems in a vastly reduced time when compared with conventional methods with the added benefit of immediate improvement in track performance

“

”Peter Musgrave, Lead Trackbed

Design Engineer, Network Rail

R Rail

A FREE Guide to Track Bed Micro Piling is for the benefit of rail industry professionals. A download of the guide can be obtained from the PWI web site: www.thepwi.org

Hertfordshire Head Office. Nexus House, Boundary Way, Hemel Hempstead, Herts HP2 7SJ.

T: 01442 236 507 F: 01442 239 096 E: info@aspingroup.com W: www.aspingroup.com

Hertfordshire • Nottinghamshire • Derbyshire • Lancashire • Staffordshire • Glasgow

The Result

At the Severn Tunnel junction, ground conditions were challenging, Aspin’s Project Manager said: “As the ballast sinks, it’s like putting a rail track on top of a mattress.” Conditions had been causing long term track stabilisation issues, adding expense and the inconvenience of remedial works.

Over a 12 week work programme, the Aspin team analysed the ground conditions and then designed and installed 198 micro pile foundations to three metres. The diameters were just 114mm so they could fit between the sleepers, avoiding the need to lift the tracks. Additional strength is provided with a wide pile cap of 275mm in diameter.

The works were completed on Saturday nights during 12 possessions and in five hour shifts, with up to 30 piles completed in just one night.

The Solution

Following completion of the works, no further track bed stabilisation remedial works were required at the site and safe and comfortable travel is permitted up to the line speed of 75mph.

Aspin’s micro piling solutions have been developed in partnership with Network Rail and are proven in five locations. It’s the subject of extensive interest as a rail solution for difficult ground conditions in the UK and potentially world-wide. It’s explored more fully in the new, free Guide to Track Bed Micro Piling.

Co-author of the Guide, Peter Musgrave, Network Rail’s Lead Track Bed Design Engineer, explained:“There’s lots of interest in micro piling within Network Rail and its ability to help solve long term problems quickly and with minimally intrusive works. Our new guide addresses micro piling in its entirety - covering site identification, investigation techniques, design and construction applying the asset management process (AMP) and will be used to inform other engineers within our organisation as well as having potential applications worldwide,” he said.

PIONEERING

IN ONE NIGHT

PARTNERSHIP197 30NEW

MICRO PILES

17CS March 2018